The criticism came after the Scottish government announced that Anglian Water Business (AWB) had been awarded the £80 million contract to look after water bills for Scotland’s schools, hospitals and other public buildings.

Cabinet Secretary for Infrastructure, Investment and Cities Keith Brown described the contract as: “The best deal for Scotland, and this contract will save public bodies up to £10m annually

“But we have ensured that Scottish Water remains in public hands, and we have secured the best possible deal to ensure Scotland benefits.”

Mr Watson commented: ““UNISON is deeply disappointed that the contract for Scotland’s public sector water and wastewater services is to be awarded to a privatised utility. We have always said that Scottish water should stay in Scotland in public hands it works, is good value for money and water customers support the corporation staying in public hands.”

Mr Rennie added: “This is a private sector deal from a government which has told us it is utterly against such a thing.

“The simple fact is that this deal will see Scottish taxpayers hand profits to a private sector group. The real beneficiaries of this deal are the investors in Australia and Canada who own the vast bulk of Anglian Water Business.”